1. Field of the Invention
The invention relates to a synchronizing device for the parallel connection of a synchronous generator and an a.c. network. A measuring circuit is employed for mesuring the voltage and the frequency from the generator and of the a.c. network and for measuring the phase angle between the network and the generator voltage. The measuring circuit includes control outputs for rpm regulation of the generator drive to adjust the actual value of the generator frequency to a set value range matched to the network frequency. The measuring circuit is also employed for voltage regulation of the generator to adjust of the generator voltage to the network voltage. A with a switching command output is provided for a coupling switch which, in the course of a set value adjustment of the voltage and frequency as a function of a set value adjustment of the phase angle, can be triggered by means of a predetermined set value calculated by a computer from the frequency difference and the predeterminable switching time of the coupling switch.
2. Discussion of the Background of the Invention and Material Information
Until a few years ago it was customary to synchronize two a.c. or rotary current networks by means of a double voltage or difference voltage for example, a double reed frequency meter and a rotating phase angle meter, i.e., the so-called synchronoscope. The correct and recurring synchronization time can be read off the phase angle meter. The most important prerequisite for connecting two a.c. networks (or a generator and an a.c. network) is that the time values of the voltages must agree at the time of the connection. This means that the effective values of the conductor voltages, the frequencies, the phase position and the phase sequence of the voltages must be the same.
It is almost impossible to manually set the frequency of the generator voltage exactly to the frequency of the a.c. network; for this reason beats occur. Two a.c. networks can be connected or a generator can be connected to an a.c. network, during each zero passage of the beat, wherein the time values of the voltages agree and which is the synchronization time.
In the course of manual synchronization, the skill and the experience of the operating personnel determine how closely to the ideal synchronization time a generator is connected to the a.c. network. If synchronization takes place fully automatically by constant measurement of the difference voltage, i.e., the difference frequency and the phase shift between the two voltages, it is possible to determine the synchronization time fairly accurately. Because the individual measurements by the known devices take place analogously, it is not possible to perform a switching operation optimally at the next synchronization time.
To assure stable and rapid synchronization of a synchronous generator with an arbitrary generator drive, a synchronizing device was proposed in Austrian application oA 820/88, published on Jul. 15, 1992. A measuring circuit for determining parameters for the dependence of the chronological rpm variation of the generator drive on a control signal action of its rpm regulation, and a memory for these parameters were proposed. From the stored parameters a computer can then calculate the size of the control signal for the desired rpm change necessary for a frequency adjustment. The measuring circuit was not described in detail nor were details given as to the times this measuring circuit stores the parameters in the memory. The specification merely mentioned that dependence of the chronological rpm variation can be detected by means of a control signal action on the rpm control via the frequency measurement.